Synthesis of N-ethyl Carbazole Carbazole Dye

0.25 g (0.001 mmol) of N-ethyl carbazole carboxaldehyde was taken in 10 ml of absolute methanol was stirred at 60 °C for 30 min. Subsequently, 0.5 g (0.003 mmol) of barbituric acid was gradually added with continuous stirring. The reaction mixture was then stirred for 10–12 h at 60 °C. Following the reaction's completion, the precipitated solid was filtered and rinsed with pre-cooled ethanol. The obtained dye underwent additional purification through recrystallization in a dichloromethane (DCM)/methanol mixture, yielding a pure yellow solid.
Yield 85 %, ¹H NMR (400 MHz, DMSO‑d₆, ppm), 11.30 (s 1H), 11.19 (s 1H), 9.30 (d, 1H), 8.65 (dd, 1H), 8.54 (s, 1H), 8.20 (d, 1H), 7.75 (m, 2H), 7.57 (t, 1H), 7.34 (t, 1H), 4.53 (m, 2H), 1.38 (t, 3H). ¹³C NMR (100 MHz, DMSO‑d₆, ppm): 168.3, 164.8, 163.0, 157.4, 150.8, 143.2, 140.8, 133.9, 130.1, 127.3, 124.0, 123.0, 122.8, 121.1, 121.0, 114.6, 110.6, 109.6, 40.1, 40.0, 39.8, 14.3, CHN Analysis analytical calculated for C₁₉H₁₅N₃O₃: C - 68.46; H - 4.54; N - 12.61. found C - 68.43; H - 4.57; N - 12.59. Mass: HRMS 334.1192 [M+1].